class Test
	{
	public static void main(String[] args)
		{
		Fly f1 = new Aeroplane();
		Fly f2 = new Helicopter();
		//Fly f3 = new Jet();
		Jet j = new Jet();
		f1.start();
		f1.inAir();
		f1.land();
		f1.refill();
		f2.start();
		f2.inAir();
		f2.land();
		f2.refill();
		j.start();
		j.land();
		}
	}
	
abstract class Fly
	{
	public abstract void start();
	public abstract void inAir();
	public abstract void land();
	public static void refill()
		{
		System.out.println("50 litres refilled");
		}
	}
class Aeroplane extends Fly
	{		
	public void start()
		{
		System.out.println("Plane is starting");
		}
	public void inAir()
		{
		System.out.println("Plane is in air");
		}
	public void land()
		{
		System.out.println("Aeroplane Landing");
		}
	}
	
class Helicopter extends Fly
	{
	public void start()
		{
		System.out.println("Helicopter is starting");
		}
	public void inAir()
		{
		System.out.println("Heloicopter is in air");
		}
	public void land()
		{
		System.out.println("Helicopter is landing");
		}
	}

class Jet 
	{
	public void start()
		{
		System.out.println("Jet is starting");
		}
	/*public void inAir()
		{
		System.out.println("Jet is in air");
		}*/
	public void land()
		{
		System.out.println("Jet is landing");
		}
	}
		